import Vue from 'vue';

export default function scrollIntoView(container, selected) {
    if (Vue.prototype.$isServer) return;

    if (!selected) {
        container.scrollTop = 0;
        return;
    }

    const offsetParents = [];
    let pointer = selected.offsetParent;
    while (pointer && container !== pointer && container.contains(pointer)) {
        offsetParents.push(pointer);
        pointer = pointer.offsetParent;
    }
    const top = selected.offsetTop + offsetParents.reduce((prev, curr) => (prev + curr.offsetTop), 0);
    const bottom = top + selected.offsetHeight;
    const viewRectTop = container.scrollTop;
    const viewRectBottom = viewRectTop + container.clientHeight;

    if (top < viewRectTop) {
        container.scrollTop = top;
    } else if (bottom > viewRectBottom) {
        container.scrollTop = bottom - container.clientHeight;
    }
}
